This project is directed at extending our knowledge concerning the physiology of surface-induced deep hypothermia with the objectives of improving its quality and extending the safe duration of circulatory arrest as an adjunct to open heart surgery in infants. A second goal is to develop new operations for the treatment of congenital heart disease. Specific work to be done in the coming year includes: development of a more efficient thrombo-resistant heat exchanger for heparinless bypass, extending the safe limit of circulatory arrest to 90 minutes by including deeper levels of hypothermia with heparinless bypass; evaluation of changes in platelet function, viscosity, distribution of cardiac output, oxygen consumption, and myocardial function during hypothermia and the influence of various anesthetics and rewarming techniques on some of these parameters; validating the thermaldilution method of cardiac output determination during hypothermia; elucidating the neuropathologic basis of the "high stepping" gait; attempting to modify skeletal muscle so it may be successfully transplanted into the right ventricle; evaluation of the function and viability of autologous atrial patches in the right ventricle; and determining the growth potential of pulmonary valve autografts in the aortic root. BIBLIOGRAPHIC REFERENCES: Ishitoya, T., Sato, S., DiBenedetto, G., Vanini, V., Mohri, H., Merendino, K.A. and Dillard, D.H. "Oxygen consumption during surface-induced deep hypothermia under halothane anesthesia." Ann. Thor. Surg. 23:52-57, January, 1977. Dillard, D.H., Mohri, H., and Merendino, K.A. "Prefabricated dacron baffle for use in correction of transposition of the great arteries." Ann. Thor. Surg. 18:204-208, March 1977.